Among Methadone Patients With Psychiatric Conditions, Only Cannabis Use Was Elevated | Research

The takeaway

In 588 methadone-treated patients, 63.5% had a lifetime psychiatric diagnosis, but dual diagnosis was associated only with increased cannabis use, not opioid, cocaine, or alcohol use.

Addiction medicine clinicians, dual diagnosis researchers, opioid treatment providers

29% increase in cannabis use among dual-diagnosis methadone patients

What the researchers found

Among 588 patients receiving opioid agonist treatment with methadone, 63.5% had a lifetime dual diagnosis and 83.5% reported past-month substance use. Having a psychiatric comorbidity was not associated with increased use of opioids, cocaine, or alcohol, but was associated with a 29% increase in cannabis use (PR=1.29).

Why it matters

Understanding why cannabis is the only substance elevated among dual-diagnosis methadone patients could inform treatment. It suggests cannabis may serve a different role than other substances for people managing both opioid use disorder and psychiatric conditions.

The numbers in context

588 patients (20% women, mean age 48.4). 63.5% lifetime dual diagnosis. 83.5% past-month substance use. Cannabis was the only substance with elevated use among dual-diagnosis patients (PR=1.29). Opioid, cocaine, and alcohol use showed no significant difference.

How the study worked

Cross-sectional study of 588 convenience-sampled patients from eight outpatient drug treatment centers in Catalonia, Spain. Dual diagnosis assessed using the Dual Disorder Screening Interview. Self-reported substance use evaluated via questionnaire. Poisson regression models adjusted for sociodemographic, clinical, and treatment variables.

What this study cannot tell us

Cross-sectional design from one region of Spain. Convenience sample may not represent all methadone patients. Self-reported substance use. Lifetime diagnosis doesn't capture current symptom severity.

How to read the evidence

Moderate: multi-site study with validated screening tools, but cross-sectional design and convenience sample

When this study was published

Published in 2025

The bigger picture

The selective association between psychiatric comorbidity and cannabis use (but not other substances) in methadone patients may reflect self-medication patterns. Cannabis might be perceived as less harmful or more accessible than other substances for managing psychiatric symptoms.

Questions still open

Are patients with dual diagnoses using cannabis to self-medicate psychiatric symptoms? Does cannabis use in this population improve or worsen psychiatric outcomes? Would addressing the psychiatric condition reduce cannabis use?

Common questions

Why is cannabis use specifically elevated in dual-diagnosis patients?

The study found the association but could not explain the mechanism. The authors suggest that methadone's pharmacological effects and the comprehensive treatment approach may adequately manage cravings for opioids, cocaine, and alcohol, while cannabis use may be driven by different factors.

Does this mean cannabis is a problem for methadone patients?

The study showed elevated use but did not assess whether cannabis helped or harmed treatment outcomes. Whether cannabis use in this population is harmful, neutral, or potentially beneficial remains an open question.

Read the original research

Association of Lifetime Psychiatric Comorbidity and Current Substance Use in Methadone-Treated Individuals with Opioid Use Disorders.

Journal of dual diagnosis, 21(4), 267-279

View on PubMed ↗Publisher’s paper ↗

Citation

Barbaglia, M Gabriela; Molero-Calafell, Javier; Angulo-Brunet, Ariadna; Alcaraz, Saül; Bartroli, Montse; Mestre-Pintó, Joan I. (2025). Association of Lifetime Psychiatric Comorbidity and Current Substance Use in Methadone-Treated Individuals with Opioid Use Disorders.. Journal of dual diagnosis, 21(4), 267-279. https://doi.org/10.1080/15504263.2025.2557191